Classic components – Spokes

Although Gottlieb Daimler and Wilhelm Maybach’s Einspur, the world’s first petrol driven motorcycle, had wooden spoked wheels, and many modern machines have aluminium or other alloy cast spoked wheels, for the rest of us, our machines use wire wheels.

Wire wheels have a number of disadvantages, including they aren’t stiff enough under side loads, suffer from fatigue and their concentricity may be poor. Advantages include they require minimal materials, are often strong, resilient to road bumps and, most importantly, are light. Apart from their lightness helping minimise a motorcycle’s weight, it also minimises the unsprung weight of motorcycles with sprung front forks and rear suspension, key to good roadholding.

In the past we’ve looked at wheel rim types and choices – now we examine spokes.

Materials:

Traditionally, spokes were manufactured in steel, then cadmium, nickel or chrome plate finished or painted. Today, most spokes are manufactured in stainless steel, with options of finish including polished and dull, bright mild steel for finish by the customer (e.g. paint, nickel plate, chrome plate or anodising) or supplied in galvanised (zinc plated) or matt black bright mild steel. For scrambling/motocross, some suppliers offer stronger spokes in differing materials.

Spoke nipples are commonly supplied in steel for customers to finish, or with galvanised, anodised or nickel plate finishes. Other options include brass finished in nickel plate (favoured by some for stainless steel spokes) or stainless steel.

Spoke kits for some Japanese and Continental machines may have chrome plated spokes and nipples.

Spoke threads

Commonly, spokes threads are applied using hardened dies (usually three) fitted to a holder applied rotationally to the spoke’s cylindrical surface. In operation, the dies in the holder are rotated about the cylindrical metal surface, which reshapes it under pressure, creating the thread.

Whole rolled threads are today’s norm. Some motorcycle wheel spokes in the past had their threads cut with dies in the same way stud and bolt threads can be created. This is an important consideration as the identical gauge spoke will offer differing spoke thread O/D, dependent on how the thread is formed; cut thread have a smaller O/D than rolled threads and require different thread size nipples.

Measuring

Commonly, spokes are sold by length and gauge (see table) or measured diameter. Most spoke suppliers supply by overall length of the, spoke but a few measure from inside the neck angle, which is confusing…

Neck (bend) angle, near head

Commonly, options are straight, 45 degree or 90 degree angle.

Spoke types

The three common types are single gauge (so same diameter the entire spoke length excepting the head), single butt spokes (larger diameter of spoke near the head and for some length – perhaps a quarter of spoke) then waists to a smaller diameter and double butt spokes (butt at both head and thread ends) while waisted in the middle. In all cases, the waisted and butted lengths are parallel.

Spoke diameters

Spoke gauge sizes comply with the Standard Wire Gauge (SWG), though Imperial or metric measurements for the diameter will be employed by some spoke suppliers. Note TPI (threads per inch).

Notes:

*Spokes supplied may vary marginally from above diameters, but so long as you buy spokes and nipples as sets, you are home and dry.

*For butted spokes, the butt’s diameter and waisted length diameter need quoting. Often, the supplier will only be able to provide their nearest as making one-off sets of butted spokes isn’t cost effective.